Burning and collection apparatus for combustion gases

ABSTRACT

A burning and collection apparatus for combustion gases, comprising a combustion unit having a combustion chamber in which a sample material is to be burned and an electric heating furnace, a gas supply unit for introducing air or gas at an optionally adjusted predetermined rate, a piston-cylinder type gas collection unit for collecting the combustion gases generated in said combustion chamber, and a driving unit for operating said piston at an optionally adjusted predetermined speed, whereby a sample material such as plastics can be burned under an optional temperature and an optional supply rate of air, and the resulting combustion gases can be collected without substantially diluting them and hence the composition of the combustion gases can be analyzed with high accuracy.

United States Patent [191 Takeyama et a1.

[ 51 Sept. 9, 1975 BURNING AND COLLECTION APPARATUS FOR COMBUSTION GASES[73] Assignee: Matsushita Electric Industrial Co.,

Ltd., Kadoma, Japan [22] Filed: Mar. 5, 1973 [21] Appl. No.: 338,194

3,529,937 9/1970 Ihara ct al 23/253 PC 3,542,121 11/1970 Koartinen23/253 PC UX 3,811,839 5/1974 DiPietro et al. 23/253 PC PrimaryExaminer.loseph Scovronek Attorney, Agent, or Firm-Stevens, Davis,Miller & Mosher [5 7] ABSTRACT A burning and collection apparatus forcombustion gases, comprising a combustion unit having a combustionchamber in which a sample material is to be burned and an electricheating furnace, a gas supply unit for introducing air or gas at anoptionally adjusted predetermined rate, a piston-cylinder type gascollection unit for collecting the combustion gases generated in saidcombustion chamber, and a driving unit for operating said piston at anoptionally adjusted predetermined speed, whereby a sample material suchas plastics can be burned under an optional temperature and an optionalsupply rate of air, and the resulting combustion gases can be collectedwithout substantially diluting them and hence the composition of thecombustion gases can be analyzed with high accuracy.

4 Claims, 4 Drawing Figures BURNING AND COLLECTION APPARATUS FORCOMBUSTION GASES This invention relates to a burning and collectionapparatus for combustion gases, which is used in analyzing thecomposition of the combustion gases generating upon burning a samplematerial such as plastics, by burning the sample material and collectingthe combustion gases.

In recent years, building fire in which many human lives are lost is oneof the social problems. It is said that such casualty is caused by,among others, the toxic gases generating by the combustion of plasticmaterials, such as carbon monoxide, hydrogen cyanide, hydrogen chloride,phosgene, carbonyl sulfide, etc. It is, therefore, desired toselectively use plastic materials for particular applications whiletaking into account the composition of the combustion gases which eachplastic material will generate at the time of fire. The combustion gasesgenerated when a material is burned contain gases which are generated bythe burning of the material with flames and gases which are generated bythe thermal decomposition of the material without accompanying flames.Thus, it is necessary, in determining the composition of the combustiongases generating from a plastic material at the time of fire, todetermine the compositions of both types of gases, Many reports huVCbeen made concerning the composition of the gases which are generatedwhen plastic materials are subjected to thermal cracking in an inert gasatmosphere or under reduced pressure, but few reports have been madeconcerning the composition of the gases which are generated when plasticmaterials are burned or subjected to chemical change accompanying lightand heat.

Conventional burning and collection apparatus used for the compositionanalysis of combustion gases are classified broadly into the followingtypes:

I. A type in which a sample material is burned in the atmosphere and theresulting combustion gases are collected in a large container disposedabove the sample material by taking advantage of the ascending anddissipation of the combustion gases.

I]. A type in which a sample material is heated by an electric heater ina flask having air or an inert gas such as nitrogen gas sealed therein,and the resulting gases are collected in the flask and a balloonconnected to said flask for relieving the pressure building up in saidflask.

III. A type in which a sample material placed in a magnetic boat with aniron piece attached thereto is inserted in a combustion tube, located ata heating por tion in said combustion tube by shifting said magneticboat externally by means of a magnet and burned at said heating portionin air or an inert gas, such as nitrogen gas, introduced into saidcombustion tube at a pre' determined rate, and the resulting combustiongases are collected in a flask which has previously been reduced inpressure.

However, the apparatus of the type I has had the disadvantages that thecomposition analysis cannot be achieved with high accuracy since thecombustion gases are diluted with a large quantity of air, and that thecombustion is possible only in air and the atmospheric gas cannot bechanged optionally. The apparatus of the type II has suffered thedisadvantage that when the material is burned in the flask in which issealed air, the oxygen concentration in the flask decreases as theburning proceeds and pressure is built up in said flask by generatedgases though the balloon is inflated, so that it is impossible to burnthe material under the same conditions from the start to end of theburning. The apparatus of the type III has had the disadvantages thatthe regulation of the supply rate of air or inert gas relative to thedecreasing pressure in the flask is difficult and hence the combustionconditions can hardly be maintained constant, namely if the supply rateof air or inert gas is too high, combustion under pressurized state willresult while conversely, if the supply rate is too low, combustion underreduced pressure state will result, and that, therefore, the combustionconditions vary between the start and end of combustion though not tosuch a large degree as in the apparatus of the type II.

An object of the present invention is to provide a burning andcollection apparatus for combustion gases in which a sample material canbe burned under the same conditions from the start to end of thecombustion and the resulting combustion gases can be collected withoutsubstantially diluting them.

Another object of the invention is to provide a burning and collectionapparatus for combustion gases, in which the temperature of a combustionchamber and the supply rate of air or inert gas to said combustionchamber can optionally be adjusted, and various combustion conditionscan be reproduced.

Still another object of the invention is to provide a burning andcollection apparatus for combustion gases, in which, in the event whenthe combustion gases generated are soluble in water, the combustiongases can be collected substantially entirely in the gaseous statewithout dissolving them in water, such as moisture.

A further object of the invention is to provide a burning and collectionapparatus for combustion gases, in which an air having an oxygenconcentration different from the atmospheric air, or an inert gas, suchas nitrogen gas, is used in lieu of the atmospheric air, wherebycombustion gases in different atmospheres can be collected.

Namely, the burning and collection apparatus according to the inventionis characterized in that it comprises a combustion unit consisting of acombustion chamber in which a sample material is to be placed and aheating furnace for heating said combustion chamber, a gas supply unitfor introducing a predetermined rate of air or other gas into saidcombustion chamber, and a piston-cylinder type gas collection unit forsucking the combustion gases generated in said combustion chamber.

The combustion chamber is made preferably of materials which do notreact with combustion gases and highly resistive to heat, e.g. quartz.The heating furnace may be of electric heater type or gas burning type,but the electric heater type is preferred in view of stability and easein adjustment of the heating temperature, and sanitation. As the gassupply unit, an air pump of the like is used when air in the atmosphereis to be supplied, or means for mixing nitrogen or oxygen gas in air isused when an air of oxygen concentration different from that of theatmospheric air is to be used, or a bomb containing an inert gas, suchas nitrogen gas, is used when such inert gas is to be used. However, theatmospheric air is generally used in the operation of the subjectapparatus and, therefore, the apparatus will be described hereunder ascomprising an air supply unit.

The air supply unit is preferably of a type by which the supply rate ofair per unit time can optionally be adjusted and which is capable ofsupplying air at a stable rate. Such type of air supply unit includes anair pump. a blower and a bomb. Further, when the atmospheric air is tobe supplied, it is desirable to provide dehumidization means in the airsupply line on the downstream side of the combustion chamber so thatwater-soluble gases in the combustion gases resulting from combustionmay not dissolve in water contained in air. The piston-cylinder type gascollection unit may be of a type in which a piston is moved or acylinder is moved with the piston fixed, for sucking the combustiongases generated in the combustion chamber. The piston or cylinder may beoperated either manually of by an operating device. It is essential,however, that the quantity of air supplied per unit time by the airsupply unit and the quantity of gases sucked per unit time by the gascollection unit be substantially equal so as not to create a pressurizedcondition or reduced pressure condition in the combustion chamber, or tomaintain said combustion chamber at normal pressure condition. To thisend, an Operating device, such as a motor, is generally used to operatethe piston or cylinder at a constant speed. The piston or cylinderoperating device, similar to the air supply unit, is preferably of atype by which the suction rate of gas can optionally be adjusted.However, even with such operating device, it is extremely difficult tomake exactly equal the supply rate of air and suction rate of gas.Therefore, the dimensions of the piston and cylinder are selectedpreferably so as to provide therebetween sealing effect to such a degreethat, when a pressure differential has occurred between the interior andexterior of the cylinder upon displacement of either the piston orcylinder relative to each other, air may move into the cylinder toeliminate the pressure differential, whereas when a pressuredifferential has not occurred, the movement of air may be blocked, andthereby to maintain the suction rate of gas slightly larger than thesupply rate of air. If the suction rate of gas is simply made slightlylarger than the supply rate of air, a reduced pressure condition willappear in the combustion chamber. However, by selecting the dimensionsof the piston and cylinder as described above, a slight amount of airflows into the cylinder as the internal pressure of the cylinder tendsto decrease below the atmospheric pressure at the time of suctionoperation, whereby the development of sub-atmospheric pressure in thecylinder and combustion chamber can be prevented and substantialdilution of the collected gases can be avoided, and further theadjustment of the operating speed of the operating device can befacilitated. The inner walls of the cylinder and piston which arecontacted by the combustion gases should be coated with materials littlereactive with the gases, e.g. fluorine-containing resin andpolyethylene, or the cylinder and piston should be made of suchmaterials, so that said inner Walls may not be attacked by thecombustion gases. Water-soluble combustion gases may be generatedoccasionally depending upon the type of sample material burned. If theaqueous vapour generated in the combustion chamber on such occasion arecollected in the cylinder along with other combustion gases, thewater-soluble gases will be dissolved in the water formed in thecylinder upon cooling of the aqueous vapour. Thus, the gases insolublein water will be collected in the gaseous state and the gases soluble inwater in the form of solutions in water, so that the subsequent analysisof gas composition cannot be completed at once. It is, therefore,recommended to provide between the combustion chamber and gas collectionunit cooling means for cooling the gases to be collected and liquefyingthe aqueous vapour entrained therein, and thereby to remove the waterfrom the gases so as not to be collected in the gas collection unit. Asthe cooling means, a conduit connecting the combustion chamber with thecylinder may be elongated so that the aqueous vapour may be cooled andcondensed by the external air during passage in said elongate eonduit.It is possible to contact cold water with the outer surface of theconduit to forcibly cool and condense the aqueous vapour. Further, it isadvantageous, for enhancing the accuracy of analysis, to provide filtermeans in the conduit between the combustion chamber and cylinder toremove smoke and soot from the combustion gases before they arecollected in the cylinder.

FIG. I is a diagram showing the layout of an embodiment of the burningand collection apparatus for combustion gases, according to theinvention;

FIG. 2 is a sectional view of the combustion unit of the apparatus,showing the arrangement to measure the temperature of said combustionchamber;

FIG. 3 is a sectional view of the piston-cylinder type gas collectionunit; and

FIG. 4 is an end view of the gas collection unit.

Now, an embodiment of the present invention will be described withreference to the drawings.

In the drawings, reference numeral 1 designates a combustion unit inwhich sample materials such as plastics are to be burned. The combustionunit 1 includes a quartz cylindrical combustion chamber 2 and a heatingfurnace 3 surrounding said combustion chamber '2 externally. Thecombustion chamber 2 has an inner diameter of 46 mm and a height of 220mm, and is provided at its bottom with a gas inlet port 4 extendingoutwardly through the heating furnace 3 and at its top with a gas outletport 5 and a sample supply port 7 which is opened and closed by a cap 6.Quartz beads 8 are filled in the combustion chamber 2 up to a level 75mm from the bottom of said chamber. The heating furnace 3 has an innerdiameter of 60 mm and a height of 200 mm, and is provided with anelectric heater therein. Namely, the heating furnace 3 is of so-calledelectric heating type. Reference numeral 9 designates an air supply unitfor supplying air to the inlet port 4 of the combustion chamber 2. Thisair supply unit 9 consists of an air pump of a type in which the supplyrate of air per unit time is adjustable, and is connected to the inletport 4 by a gas supply passage 10. Reference numeral 11 designates adehumidization unit provided in the gas supply passage 10 and consistsof a tank 12 with desiceants such as silica gel 13 disposed therein. Asection of the gas supply passage 10 leading from the air pump 9 isopened in the bed of silica gel 13 and another section of said gassupply passage 10 leading to the combustion chamber 2 is extended fromthe top of the tank 12 spaced above the bed of silica gel 13. In the gassupply passage 10 on the downstream side of the dehumidization unit 11is provided a flow meter 14 which indicates the quantity of air suppliedto the combustion chamber 2 in a unit time. Reference numeral 15designates a piston-cylinder type gas collection unit for collecting thecombustion gases generating in the combustion chamber 2. This gascollection unit consists of a cylindrical cylinder 17 communieating withthe gas outlet port 5 of the combustion chamber 2 through a gas exhaustpassage 16, and a piston 18 disposed in said cylinder 17 for slidingmovement therein. The cylinder 17 has a cross-sectional area of 177 cm'and an internal volume of 4 l, and is made of stainless steel. The innerwall of the cylinder 17 is lined with a coating film 19 of a materiallittle reactive with the combustion gases collected, e.g. polytetrafluoroethylene or polyethylene. The piston 18 is provided with arope-shaped seal ring 20 which is made of a tetrafluoroethylene having aShore hardness of 50-65 and mounted on the outer peripheral surfacethereof in light contact with the inner surface of the cylinder 17. Theseal ring 20 provides a sealing effect between the piston 18 and thecylinder 17 to such a degree that, when a pressure differential hasoccurred between the interior and exterior of the cylinder 17 upondisplacement of the piston 18 relative to said cylinder, air ispermitted to flow into the cylinder through between the seal ring 20 andthe inner wall of the cylinder 17 to eliminate said pressuredifferential, but when the piston 18 is held stationary, air flowbetween the interior and exterior of the cylinder 17 is blocked. Theinner wall of the piston 18 which will be contacted by the combustiongases collected in the cylinder 17 is coated with a coating film 19' ofthe same material as the coating film 19. The gas exhaust passage 16 isformed of a polytetrafluoroethylene tube having an inner diameter of 8mm and a length of 1.5 In, said tube consisting of a plurality ofsections detachably coupled together by means of couplings 21. In thegas exhaust passage 16 is provided filter means 22 which consists of acylindrical casing communicating with said gas exhaust passage 16 andpacked with glass wool 23. A driving device 24 is provided to causedisplacement of the'piston 18 within the cylinder 17, which comprises amotor 25, a stepless speed change gear 26 connected with said motor 25and a guide structure 28 interconnecting said stepless speed change gear26 and a piston rod 27 of the piston 18. The guide structure 28 iscomposed of opposed fixed support plates 30, 31, an externally threadedrod 29 connected with the stepless speed change gear 26 and rotatablysupported by said support plates 30, 31, a guide rod 32 extending acrosssaid support plates 30, 31 with the opposite ends secured theretorespectively, and a movable plate 33 slidably mounted on said guide rod32 at one end with said threaded rod 29 threadably extendingtherethrough and having the piston rod 27 connected to the other endthereof.

The burning and collection apparatus for combustion gases, of theconstruction described above is operated in the following sequence:Namely, the combustion.

chamber 2 is heated by the electric type heating furnace 3 at first andthen the air pump 9 is set in motion to feed air into the combustionchamber 2, after open ing the sample material supply port 7 of saidcombustion chamber. The air supplied from the air pump 2 is dehumidizedduring passage through the dehumidization unit 11 by the silica gel 13disposed in said dehumidization unit. The dry air leaving thedehumidization unit 11 after passage through the silica gel 13 passes inthe flow meter 14 and enters the combustion chamber 2 from the gassupply port 4. The flow rate of air from the air pump 9 is regulated toa desired value, e.g. lOO l/hr. on the flow meter 14. The air enteringthe combustion chamber 2 is heated therein and discharged to the outsidefrom the sample material supply port 7. The temperature of thecombustion chamber 2 or, more specifically, the temperatures of thesurface of the quartz beads 8 and the inner wall of the combustionchamber 2 which are heated most, are measured by means of a thermocouple34 inserted into the combus tion chamber 2 from the sample materialsupply port 7, to adjust the temperature of said combustion chamber 2 toa desired value, e.g. 700C., by controlling the current being suppliedto the electric heating furnace 3. The stepless speed change gear 26 ispreviously adjusted such that the quantity of gases sucked in a unittime will be slightly larger than the quantity of air supplied in a unittime by the air pump 9, and then the motor 25 is set in motion tooperate the piston 18 for suction stroke. In this case, the externallythreaded rod 29 rotates and the moving plate 33 in threadable engagementwith said rod 29 displaces towards the motor 25 along the rod 29 and theguide rod 28, whereby the piston 18 is pulled for suction stroke.Simultaneously with starting the suction stroke, a predetermined weightof a sample material is placed in the combustion chamber 2 from thesample material supply port 7 and then said supply port 7 is closed bythe cap 6. The sample material placed in the combustion chamber 2 burnstherein generating a variety of combustion gases. The combustion gasesin most cases contain aqueous vapour. The combustion gases thusgenerated ascend in the combustion chamber 2 and are collected in thecylinder 17 through the gas exhaust passage 16. The aqueous vapourentrained in the combustion gases is cooled and condensed while thecombustion gases are passing in the gas exhaust passage 16 which isconsiderably long, and the resulting water attaches to the inner wall ofthe exhaust passage 16 and to the glass wool in the filter means 22, inthe form of water droplets. The smoke and soot resulting from thecombustion are removed from the combustion gases by the filter means 22during passage of the combustion gases in said filter means, and littleof them reach the cylinder 17. A subatmospheric pressure condition tendsto occur in the cylinder 17 and combustion chamber 2 in the suctionstroke of the piston 18 since the suction rate of gases into the gascollection unit is slightly larger than the supply rate of air from theair pump 9. In practice, however, such condition does not occur and thecylinder 17 and combustion chamber 2 are maintained at substantiallynormal pressure, because the external air flows into the cylinder 17through between the seal ring 20 mounted on the piston 18 and the innerwall of the cylinder 17. Therefore, in'no case will the rate of airsupplied into the combustion chamber 2 vary due to the pressurereduction otherwise occurring in said combustion chamber, and hence thecombustion conditions can be maintained constant. The combustion gasesare collected in the cylinder 17 at high concentrations in a shortperiod of time, e.g. l 2 minutes, after the piston 18 has ceased itsmovement without substantially being allowed to leak to the outside,though they are diluted slightly with air. Thus, the combustion gasesgenerating in the combustion chamber 2 are introduced entirely into thecylinder 17. In this case, the distance of displacement of the piston 18for suction is measured to know the total volume of the gases collected.In the experiment conducted by the present inventors, however, thepiston was pulled over a constant distance so that the total volume ofthe gases collected might be constant. It was confirmed that thecombustion gases remaining in the combustion chamber 2 could becollected entirely in the cylinder 17, by pulling the piston 18 furtherover 5 cm continuously after the completion of combustion of the samplematerial. Immediately after the combustion gases have been collected inthe cylinder 17 in the manner described, the piston rod 27 is removedfrom the moving plate 33, the section of the gas exhaust passage 16leading to the cylinder 17 is disconnected from the remaining section atthe coupling 21, a cylindrical gas cell for infrared absorptionspectrum, having an internal volume of 250 cc, a light path length of cmand a reduced pressure below 0.5 torr is connected to the disconnectedend of said section of the gas exhaust passage 16, and the combustiongases in the cylinder 17 are forced into said gas cell with pressure bypushing the piston 18 by hand. In the experiment, the pressure of thecombustiongases was returned to the atmospheric pressure just before themeasurement. It was also confirmed that the combustion gases collectedin the cylinder 17 are dissipated sufficiently within said cylinder evenright after the collec tion and segregation of gases is not seenanywhere in the cylinder.

In order to evaluate the accuracy of the subject apparatus in itscombustion gas generation and collection operation, 0.1 g of nylon 66was burned six times each under such combustion conditions that thecombustion temperature was 700C, and the supply rate of air was 100l/hr, and the quantitative analysis of the components of the combustiongases in each run was conducted by the infrared absorption spectrummethod, with the results shown in the table provided below:

In the above table numerical values are expressed in ml/g, Y representsthe mean value and C.V.(7() represents the standard deviationpercentage.

It was found that the quantities of the components other than ammoniacan be determined with the standard deviation within 10%, as shown inthe above table. The accuracy in determination of ammonia is poorprobably because ammonia is generated in a small quantity in case ofnylon 66 and also because the quantity of ammonia generated isinfluenced even by a slight change in the combustion conditions. Theaccuracy in determination of acetylene was also somewhat poor becausethe quantity of acetylene formed is varied by a slight change incombustion conditions, particularly in the supply rate of air. It wasconfirmed that the quantitative analysis of other plastics can beachieved with the same accuracy as in the case of nylon 66. Since theaccuracies depicted above include the error inherent to thedetermination by the infrared absorption spectrum, it is assumed thatthe actual accuracies is the formation and collection of combustiongases by the subject apparatus would be better than those shown in thetable provided above.

The present inventors conducted another experiment to determine theproportion in which a water-soluble gas is collected in the cylinder 17in the gaseous state when such water-soluble gas is generated in thecombustion chamber 2. In the experiment, 0.1 g of polyethylene whichgenerates a large quantity of water when burned was placed in thecombustion chamber 2 and burned therein under the same conditions underwhich it is normally burned, i.e. at a temperature of 700C. and with airsupplied at the rate of 100 I/hr. In collecting the resulting combustiongases in the cylinder 17, the aqueous vapour present therein was removedtherefrom by condensing it in the gas exhaust passage 16. Concurrentlywith the completion of combustion, 6.06 cc of ammonia gas was introducedinto the combustion chamber from the supply port 4 along with 100 l/hror air. The ammonia gas was collected in the cylinder 17 through the gasexhaust passage 16. The quantity of ammonia gas collected in thecylinder 17 was of that introduced from the supply port 4. Thus, it willbe understood that only 10% of the ammonia gas had been dissolved inwater before the ammonia gas reached the cylinder 17. It is generallyknown that plastics or other materials which will generate water-solublegases when burned, produce less amounts of water than the aforesaidpolyethylene and that plastics generate all of the water-soluble gaseswhich are to be generated therefrom, in the initial stage of combustionin which the quantity of water produced is relatively small. In view ofthe above, it is assumed that the proportion of the water-soluble gasactually collected in the cylinder 17 would be more than The presentinvention has been described herein in terms of an embodiment in whichthe atmospheric air is introduced into the combustion chamber. It shouldbe understood, however, that according to the invention combustion undera variety of conditions can be reproduced in the apparatus byintroducing into the combustion chamber airs having oxygenconcentrations different from that in the atmospheric air, and otheroxygen-containing gases. It should also be understood that gasesresulting from thermal decomposition can be formed and collected in theapparatus by introducing inert gases, such as nitrogen gas, in lieu ofair.

As may be understood from the foregoing description, the apparatus ofthe invention is advantageous in that the supply rate of air or othergas introduced into the combustion chamber and the flow rate of thegases generated in said combustion chamber and being led to the gascollection unit can be balanced and in that the conditions under whichthe combustion or thermal decomposition is carried out can be maintainedunchanged from the start to end of the combustion or thermaldecomposition, without allowing superor subatmospheric pressure todevelop in the combustion chamber. The apparatus is also advantageous inthat the gases generated in the combustion chamber can be collected inthe gas collection unit without substantially diluting them, and hencethe analysis of gas composition can be achieved with high accuracy.

It should also be noted that according to the invention the temperatureof the combustion chamber and the supply rate of air to said combustionchamber can optionally be adjusted and a variety of combustionconditions can be reproduced. The mode of combustion of an inflammablematerial in the actual fire varies largely depending upon the state offire. For instance, inflammable materials decompose at relatively lowtemperatures in the initial stage of combustion, generating gases whichconstitute smokes. By using the apparatus of the invention, the gasgenerating states under various conditions can be known by changing thetemperature of the combustion chamber. In the case of fire in buildings,air is short in most cases, whereas in the case of fire of wooden housesair is supplied sufficiently in most cases. With the apparatus of theinvention, the combustion under various conditions can be reproduced bychanging the supply rate of air to the combustion chamber in the lightof the foregoing facts.

It is an additional advantage of the invention that, since the gasexhaust passage is provided between the combustion chamber and cylinder,which has a cooling effect sufficient to condense aqueous vapour and bywhich water is prevented from being collected in the cylinder,water-soluble gases can be collected in said cylinder substantiallyentirely in the gaseous state even if such gases are generated in thecombustion chamber, and therefore, the quantitative analysis of thewatersoluble gases can be achieved simply by the same method as that forthe quantitative analysis of other combustion gases or thermaldecomposition gases.

It should also be noted that in the apparatus of the in- .vention thegeneration and collection of combustion gases and thermal decompositiongases in a variety of atmospheres are possible by supplying into thecombustion chamber airs having oxygen concentrations different from thatin the atmospheric air or inert gases such as nitrogen gas, besides theatmospheric air.

What is claimed is:

1. A burning and collection apparatus for combustion gases, comprisingcombustion means having a combustion chamber for placing sample materialtherein and an electric heating furnace capable of adjustably heatingsaid combustion chamber, gas supply means for supplying air or other gasinto the combustion chamber at an adjustable rate, piston-cylinder typegas collection means having a cylinder communicating with the combustionchamber by a gas exhaust passage having a cooling effect sufficient tocondense aqueous vapor and a piston disposed slidably in said cylinder,the gas being collected in a collection chamber defined by said pistonand the interior of said cylinder, driving means for creating relativemovement between the piston and cylinder at an adjustable predeterminedspeed and in a direction causing suction of the combustion gases intothe collection chamber so that said suction is at a rate correspondingto the supply rate of air or other gas into the combustion chamber, thedimensions of said cylinder and piston being such that sealing iscreated between said cylinder and piston wherein gas is allowed to flowinto said collection chamber between said cylinder and said piston toeliminate the pressure differential between the interior and exterior ofsaid cylinder caused by the sucking of said combustion gases by saidpiston, and when combustion gases are not being sucked, gas flow betweensaid piston and said cylinder is prevented.

2. A burning and collection apparatus for combustion gases, comprisingcombustion means having a combustion chamber for burning a samplematerial received therein and a heating furnace for adjustably heatingthe sample material in said combustion chamber, gas supply means forleading to an inlet of said combustion chamber air or other gas at apredetermined and adjustable rate, dehumidizing means for removingmoisture from the combustion gases exciting through an outlet of saidcombustion chamber by cooling said combustion gases and thus condensingan aqueous vapor contained therein, a cylinder for receiving thecombustion gases from said dehumidizing means and a piston slidablyfitted in said cylinder, said piston and said cylinder defining acollection chamber, driving means for displacing said piston at apredetermined and adjustable rate in a direction to cause suction of thecombustion gases into said collection chamber, said piston beingprovided on its outer periphery with seal ring means which is in lightcontact with the inner surface of said cylinder, so that gas is allowedto flow past said ring into said collection chamber when a pressuredifferential is created across said ring due to the suction in saidcollection chamber caused by the displacement of said piston and flow ofgas past said ring is prevented when said piston is stationary.

3. The apparatus of claim 2 wherein said cylinder is open to theatmosphere at one end, and said piston forms a single collection chamberwith the inside and the other end of said cylinder for collecting saidcombustion gases by suction at a rate equal to the supply rate of air orother gas into said combustion chamber, said sealing ring allowing flowof gas into said collection chamber from the atmosphere whendisplacement of said piston causes suction in said collection chamberand preventing flow communication of gases between the atmosphere andthe collection chamber between said cylinder walls and said piston whensaid piston is stationary.

4. A method of producing and collecting combustion gases comprising:

heating sample material in a combustion chamber;

supplying air or other gas at a predetermined and adjustable rate intosaid combustion chamber to burn the sample;

removing moisture from the combustion gases produced in said combustionchamber which gases have exited through an outlet of said combustionchamber; and

collecting said dehumidified combustion gases at substantially constantpressure and at a rate corresponding to the rate of supply of air orother gas into the combustion chamber, said collection taking place in acollection chamber defined by a movable piston and a cylinder having aseal between said piston and cylinder for maintaining substantiallyconstant pressure in said collection chamber by allowing gases atatmospheric pressure to enter said collection chamber when suction iscreated therein by movement of said piston and preventing flow of gaspast said seal when said piston is stationary.

1. A BURNING AND COLLECTION APPARTUS FOR COMBUSTION GASES, COMPRISINGCOMBUSTION MEANS HAVING A COMBUSTION CHAMBER FOR PLACING SAMPLE MATERIALTHEREIN AND AN ELECTRIC HEATING FURNACE CAPABLE OF ADJUSTABLY HEATINGSAID COMBUSTION CHAMBER, GAS SUPPLY MEANS FOR SUPPLYING AIR OR OTHER GASINTO THE COMBUSTION CHAMBER AT AN ADJUSTABLE RATE, PISTON-CYLINDER TYPEGAS COLLECTION MEANS HAVING A CYCLINDER COMMUNICATING WITH THECOMBUSTION CHAMBER BY A GAS EXHAUST PASSING HAVING A COOLING EFFECTSUFFICIENT TO CONDENSE AQUEOUS VAPOR AND A PISTION DISPOSED SLIDABLY INSAID CYLINDER, THE GAS BEING COLLECTED IN A COLLECTION CHAMBER DEFINEDBY SAID PISTON AND THE INTERIOR OF SAID CYLINDER, DRIVING MEANS FORCREATING RELATIVE MOVEMENT BETWEEN THE PISTON AND CYLINDER AT ANADJUSTALE PREDETERMINED SPEED AND IN A DIRECTION CAUSING SUCTION OF THECOMBUSTION GASES NTO THE COLLECTION CHAMBER SO THAT SAID SUCTON IS AT ARATE CORRESPONDING TO THE SUPPLY RATE OF AIR OR OTHER GAS INTO THECOMBUSTION CHAMBER THE DIMENSIONS OF SAID CYLINDER AND PISTON BEING SUCHTHAT SEALING IS CREATED BETWEEN SAID CYLINDER AN PISTON WHEREIN GAS ISALLOWED TO FLOW INTO SAID COLLECTION CHAMBER BETWEEN SAID CYLINDER ANDSAID PISTON TO ELIMINATE THE PRESSURE DIFFERENTIAL BETWEEN THE INTERIORAND EXTERIOR OF SAID CYCLINDER CAUSED BY THE SU KING OF SAID COMBUSTIONGASES BY SAID PISTON, AND WHEN COMBUSTION GASES ARE NOT BEING SUCKED,GAS FLOW BETWEEN SAID PISTON AND SAID CYLINDER IS PREVENTED.
 2. Aburning and collection apparatus for combustion gases, comprisingcombustion means having a combustion chamber for burning a samplematerial received therein and a heating furnace for adjustably heatingthe sample material in said combustion chamber, gas supply means forleading to an inlet of said combustion chamber air or other gas at apredetermined and adjustable rate, dehumidizing means for removingmoisture from the combustion gases exciting through an outlet of saidcombustion chamber by cooling said combustion gases and thus condensingan aqueous vapor contained therein, a cylinder for receiving thecombustion gases from said dehumidizing means and a piston slidablyfitted in said cylinder, said piston and said cylinder defining acollection chamber, driving means for displacing said piston at apredetermined and adjustable rate in a direction to cause suction of thecombustion gases into said collection chamber, said piston beingprovided on its outer periphery with seal ring means which is in lightcontact with the inner surface of said cylinder, so that gas is allowedto flow past said ring into said collection chamber when a pressuredifferential is created across said ring due to the suction in saidcollection chamber caused by the displacement of said piston and flow ofgas past said ring is prevented when said piston is stationary.
 3. Theapparatus of claim 2 wherein said cylinder is open to the atmosphere atone end, and said piston forms a single collection chamber with theinside and the other end of said cylinder for collecting said combustiongases by suction at a rate equal to the supply rate of air or other gasinto said combustion chamber, said sealing ring allowing flow of gasinto said collection chamber from the atmosphere when displacement ofsaid piston causes suction in said collection chamber and preventingflow communication of gases between the atmosphere and the collectionchamber between said cylinder walls and said piston when said piston isstationary.
 4. A method of producing and collecting combustion gasescomprising: heating sample material in a combustion chamber; supplyingair or other gas at a predetermined and adjustable rate into saidcombustion chamber to burn the sample; removing moisture from thecombustion gases produced in said combustion chamber which gases haveexited through an outlet of said combustion chamber; and collecting saiddehumidified combustion gases at substantially constant pressure and ata rate corresponding to the rate of supply of air or other gas into thecombustion chamber, said collection taking place in a collection chamberdefined by a movable piston and a cylinder having a seal between saidpiston and cylinder for maintaining substantially constant pressure insaid collection chamber by allowing gases at atmospheric pressure toenter said collection chamber when suction is created therein bymovement of said piston and preventing flow Of gas past said seal whensaid piston is stationary.